It is known that extrusion devices are used in order to generate a plastic melt. This plastic melt can be continued to be used in different manners. Thus, it is for example possible to introduce the molten material in a cavity of an injection molding device in order to generate corresponding components by injection molding. Likewise, it is known that the molten material is provided for a so called blow extrusion method with which a blow film is extruded. In all cases it is necessary that at the end of the extruder the liquefied molten material is transported to the respective place of usage via corresponding melt channels. These channels can be arbitrary complex and can be particularly separated to single channels.
It is a disadvantage with known solutions of extrusion devices that they comprise a high effort for the change of material. Thus, a so called purge process has to be performed in case a change of material should occur from a first molten material to a second molten material. In case for example with a blow extrusion device a certain time a product is produced with a blue film color and subsequently a change to a transparent film color is desired initially the blue film color and the corresponding molten material has to be purged from the single melt channels. Herefore, the extrusion device is already operated with the following material until the largest part of the molten material is purged out.
Since with melt channels in the edge area of these melt channels the transport speed is mainly equal to zero the old molten material so to say sticks the purge process time consuming. With blow extrusion devices with a throughput of up to approximately 120 kg molten material per hour thereby a purge process normally takes 20 minutes until 1.5 hours. For each film layer for which a change of material should occur, this accordingly leads to 120 kg or more waist material. With multiple film layers this amount is multiplied with the amount of film layers, even if only one single film layer is purged. Therewith, waist rates of up to 1,000 kg can be reached. Simultaneously, the purge time comprises a dead time for the machine in which no usable production can occur. Accordingly, the known extrusion device with the corresponding purge method is afflicted with significant disadvantages concerning the time effort and concerning the resulting costs and the waist material.